I'd say, use the - if it helps clarify the words, for example smallwidgets doesn't need a - but wowwidgets probably looks better as wow-widgets and will get less typos.
3:18 am on Nov 16, 2004 (gmt 0)
keyword1-keyword2.com, for SEO reasons.
1:07 am on Nov 17, 2004 (gmt 0)
It depends on whether you expect people to type the name or if you're going to rely on SEO (organic or otherwise). I prefer the dash as it's easier to read, especially if your keywords are longer than about 4 letters each.